Method for predicting arousal level and arousal level prediction apparatus

ABSTRACT

A method for predicting an arousal level used by a computer of an arousal level prediction apparatus that predicts an arousal level of a user includes obtaining current biological information regarding the user detected by a first sensor, calculating a current arousal level of the user on the basis of the current biological information, obtaining current environment information indicating a current environment around the user detected by a second sensor, predicting a future arousal level, which is an arousal level a certain period of time later, on the basis of the current arousal level and the current environment information, and (i) issuing a notification to the user or (ii) controlling another device, on the basis of the future arousal level.

BACKGROUND

1. Technical Field

The present disclosure relates to a method for predicting an arousallevel and an arousal level prediction apparatus.

2. Description of the Related Art

A system that obtains biological information regarding a user and thatcalculates an arousal level of the user from the obtained biologicalinformation has been proposed (e.g., refer to Japanese Unexamined PatentApplication Publication No. 2013-123524 and Japanese Unexamined PatentApplication Publication No. 2009-48605). The arousal level indicates adegree of arousal, and a low arousal level indicates that the user isfeeling drowsy.

In Japanese Unexamined Patent Application Publication No. 2013-123524, amethod for determining an arousal level from a heartbeat signal obtainedas biological information is disclosed. In Japanese Unexamined PatentApplication Publication No. 2009-48605, a vehicle system is disclosedthat avoids a driver's falling asleep at a wheel by outputting an alarmsound for the driver if a current arousal level falls below a certainthreshold.

SUMMARY

In one general aspect, the techniques disclosed here feature a methodfor predicting an arousal level used by a computer of an arousal levelprediction apparatus that predicts an arousal level of a user. Themethod includes obtaining current biological information regarding theuser detected by a first sensor, calculating a current arousal level ofthe user on the basis of the current biological information, obtainingcurrent environment information indicating a current environment aroundthe user detected by a second sensor, predicting a future arousal level,which is an arousal level a certain period of time later, on the basisof the current arousal level and the current environment information,and (i) issuing a notification to the user or (ii) controlling anotherdevice, on the basis of the future arousal level.

According to the present disclosure, a method for predicting an arousallevel and an arousal level prediction apparatus capable of predicting adecrease in an arousal level of the user are provided.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium, or any selective combination thereof.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an example of the configurationof an arousal level prediction apparatus according to a firstembodiment;

FIG. 2 is a block diagram illustrating a detailed configuration of aprocessing unit illustrated in FIG. 1;

FIG. 3 is a diagram illustrating a method for predicting a futurearousal level according to the first embodiment;

FIG. 4 is a block diagram illustrating another example of theconfiguration of the arousal level prediction apparatus according to thefirst embodiment;

FIG. 5 is a flowchart illustrating an overall operation of the arousallevel prediction apparatus illustrated in FIG. 1;

FIG. 6 is a sequence diagram illustrating a procedure of the operationof the arousal level prediction apparatus illustrated in FIG. 1;

FIG. 7 is a block diagram illustrating the configuration of an arousallevel prediction apparatus according to a second embodiment;

FIG. 8 is a flowchart illustrating an overall operation of the arousallevel prediction apparatus illustrated in FIG. 7;

FIG. 9 is a diagram illustrating an example in which a relationshipbetween the duration of driving and an arousal level of a driver isupdated; and

FIG. 10 is a diagram illustrating another example in which therelationship between the duration of driving and the arousal level ofthe driver is updated.

DETAILED DESCRIPTION Underlying Knowledge Forming Basis of the PresentDisclosure

The present inventors has noticed that, in the examples of the relatedart, an arousal level of the user is undesirably increased after thearousal level of the user falls below a certain threshold. Once thearousal level of the user falls below the certain threshold, a strongstimulus is needed to increase the arousal level (arouse the user). If astrong stimulus is given to the user during driving, for example, theuser might be surprised, which might affect the driving operation.

The present disclosure is established in order to solve the aboveproblem and provides a method for predicting an arousal level and anarousal level prediction apparatus capable of predicting a decrease inthe arousal level of the user.

A method for predicting an arousal level according to an aspect of thepresent disclosure is a method for predicting an arousal level used by acomputer of an arousal level prediction apparatus that predicts anarousal level of a user. The method includes obtaining currentbiological information regarding the user detected by a first sensor,calculating a current arousal level of the user on the basis of thecurrent biological information, obtaining current environmentinformation indicating a current environment around the user detected bya second sensor, predicting a future arousal level, which is an arousallevel a certain period of time later, on the basis of the currentarousal level and the current environment information, and (i) issuing anotification to the user or (ii) controlling another device, on thebasis of the future arousal level.

According to this aspect, since the future arousal level can bepredicted, a decrease in the arousal level of the user can be predicted.As a result, a strong stimulus is not needed to increase the arousallevel, and a decrease in the arousal level of the user can be suppressedwith a mild stimulus.

Here, for example, in the predicting a future arousal level, a rate ofdecrease in the arousal level may be estimated on the basis of howlikely it is for a person to become drowsy indicated by the currentenvironment information. The future arousal level may be predicted bycorrecting the current arousal level to the arousal level the certainperiod of time later using the rate of decrease.

In addition, for example, the issuing or the controlling may beperformed only if the future arousal level is lower than a certainthreshold.

In addition, for example, the arousal level prediction apparatus may bemounted on an automobile. The certain period of time may be included ina time taken to arrive at a destination input by the user to anavigation system installed in the automobile.

Here, for example, the biological information may include informationindicating a heart rate. The current arousal level may become lower as acurrent heart rate of the user becomes lower.

In addition, for example, the first sensor may detect the current heartrate of the user using any of a milliwave sensor, a pulse oximeter, aspeckle camera, and a laser Doppler velocimeter.

In addition, for example, the first sensor may include a camera or amilliwave sensor and detect a current respiratory rate of the user bymeasuring movement of a surface of the user's body.

In addition, for example, the biological information may includeinformation indicating a respiratory rate or an amount of air breathed.The current arousal level may become lower as a current respiratory rateof the user becomes lower or a current amount of air breathed by theuser becomes smaller.

In addition, for example, the first sensor may detect the current heartrate of the user by measuring a change in a color of the user's skinusing a photodiode.

In addition, for example, the first sensor may detect the currentrespiratory rate of the user by measuring a change in a color of theuser's skin using a photodiode.

In addition, for example, the first sensor may detect the currentrespiratory rate of the user, duration of each breath, or the currentamount of air breathed by the user by measuring a current temperature ofthe user's lips or a portion under the user's nose using a radiationthermometer.

In addition, for example, the biological information may includeinformation indicating a body surface temperature of a periphery of aperson's body and a deep-body temperature. The current arousal level maybecome lower as a current body surface temperature of a periphery of theuser's body becomes closer to the deep-body temperature.

Here, the deep-body temperature may be estimated on the basis of atemperature of the user's forehead, and the temperature of the peripherymay be estimated on the basis of a temperature of the user's nose orhands or another body part.

In addition, for example, the biological information may includeinformation indicating a blood flow volume in a periphery of a person'sbody. The current arousal level may become lower as a current blood flowvolume in a periphery of the user's body becomes larger.

In addition, for example, the first sensor may detect the current bloodflow volume in the periphery of the user's body by measuring blood flowdistribution of the user using a laser speckle camera.

In addition, for example, the first sensor may calculate pulse wavevelocity on the basis of a time difference in a change in blood flowvolume between an artery of a measured body part of the user and a veinin the periphery by measuring the change in the blood flow volume in theartery of the measured body part of the user and the vein in theperiphery using a laser speckle camera or a camera.

In addition, for example, the biological information may includeinformation indicating the pulse wave velocity or blood pressure. Thecurrent arousal level may become lower as the blood pressured or thepulse wave velocity indicated by the information included in thebiological information becomes lower.

In addition, for example, the current environment information mayinclude information indicating a current illumination around the user.The rate of decrease in the arousal level may become higher as thecurrent illumination becomes lower.

In addition, for example, the current environment information mayinclude information indicating a current wind speed around the user. Ahigher rate of decrease in the arousal level may be estimated as thecurrent wind speed becomes lower.

In addition, for example, the method may further include obtaining sleepinformation indicating hours of sleep of the user of a previous day andpredicting the future arousal level on the basis of the current arousallevel, the current environment information, and the sleep information.

In addition, for example, the method may further include obtaining pastsleep information indicating hours of sleep of the user in a certainperiod of time in past and predicting the future arousal level on thebasis of the current arousal level, the current environment information,and the past sleep information.

In addition, for example, the method may further include obtaininginformation indicating an activity history of the user and predictingthe future arousal level on the basis of the current arousal level, thecurrent environment information, and the activity history.

In addition, for example, the other device may be an air conditionerinstalled in the same space in which the arousal level predictionapparatus is installed. Setting temperature or air volume of the airconditioner may be changed if the future arousal level is lower than acertain threshold.

In addition, for example, the other device may be a lighting deviceinstalled in the same space in which the arousal level predictionapparatus is installed. Brightness of the lighting device may beincreased if the future arousal level is lower than a certain threshold.

In addition, for example, the other device may be a personal computerincluding a display used by the user. A color or luminance of thedisplay of the personal computer may be changed if the future arousallevel is lower than a certain threshold.

In addition, an arousal level prediction apparatus according to anaspect of the present disclosure is an arousal level predictionapparatus including a first sensor that detects biological information,a second sensor that detects environment information indicating anenvironment around a user, a processor that calculates a current arousallevel of the user on the basis of current biological informationregarding the user detected by the first sensor and that predicts afuture arousal level, which is an arousal level a certain period of timelater, on the basis of the current arousal level and current environmentinformation detected by the second sensor, and a controller that (i)issues a notification to the user or (ii) controls another device, onthe basis of the future arousal level.

It should be noted that these general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium such as a computer-readable CD-ROM, or anyselective combination thereof.

A method for predicting an arousal level according to each ofembodiments of the present disclosure will be specifically describedhereinafter with reference to the drawings. The following embodimentsare specific examples of the present disclosure. Values, shapes,materials, components, positions at which the components are arranged,and the like described in the following embodiments are examples, and donot limit the present disclosure. Among the components described in thefollowing embodiments, ones not described in the independent claims,which define broadest concepts, will be described as arbitrarycomponents.

First Embodiment Configuration of Arousal Level Prediction Apparatus

FIG. 1 is a block diagram illustrating the configuration of an arousallevel prediction apparatus 10 according to a first embodiment.

As illustrated in FIG. 1, the arousal level prediction apparatus 10includes a biological information obtaining unit 11, an environmentinformation obtaining unit 12, a processing unit 13, a control unit 14,a communication unit 15, and a display unit 16 and predicts an arousallevel of a user. The arousal level prediction apparatus 10 is a computeror the like. A first sensor 30 detects biological information, and asecond sensor 40 detects environment information indicating anenvironment around the user.

Biological Information Obtaining Unit 11

The biological information obtaining unit 11 obtains current biologicalinformation regarding the user detected by the first sensor 30. In thepresent embodiment, the biological information obtaining unit 11 obtainsthe current biological information by communicating with the firstsensor 30 directly or through the communication unit 15. The biologicalinformation may be information indicating a heart rate, variation in aheartbeat period, a respiratory rate, the amount of air breathed, blinkspeed, the stability of respiration periods, facial expressions,movements of the user's eyes, body surface temperature distribution,body surface temperature, deep-body temperature, blood flow distributioninside the user's body, or any combination of these pieces ofinformation. The first sensor 30, which detects biological information,may be a heart rate (pulse) sensor, a respiration sensor, a thermalimage sensor, or a blood flow sensor, or may be any combination of thesesensors. Alternatively, the first sensor 30, which detects biologicalinformation, may be any combination of a milliwave sensor, a pulseoximeter, a speckle camera, a laser Doppler velocimeter, a photodiode, aradiation thermometer, a camera, a time-of-flight (TOF) sensor, amicrophone attached to the user's clothes, a thermal image sensor, and alaser speckle camera.

Specific exemplary combinations of the biological information and thefirst sensor 30 will be described hereinafter.

When Biological Information includes Information indicating Heart Rate

For example, the biological information may include informationindicating the heart rate, and a current arousal level may become loweras a current heart rate becomes lower. This is because it is known thata person tends to feel drowsy when the heart rate is low. The firstsensor 30 in this case is a heart rate sensor.

The first sensor 30 may detect the current heart rate of the user asbiological information using any of, for example, a milliwave sensor, apulse oximeter, a speckle camera, and a laser Doppler velocimeter as theheart rate sensor. The biological information obtaining unit 11 maycalculate, from a signal indicating the heart rate obtained from thefirst sensor 30, a ratio of a low-frequency (LF) component (0.04 to 0.15Hz) to a high-frequency (HF) component (0.15 to 0.4 Hz) and obtain theratio as biological information. This is because it is known that the HFcomponent decreases when a person is active and increases when theperson is not active. The ratio may be used by the processing unit 13,which will be described later, to accurately calculate the currentarousal level of the user.

When Biological Information includes Information indicating RespiratoryRate or Amount of Air Breathed

Alternatively, for example, the biological information may includeinformation indicating the respiratory rate or the amount of airbreathed, and the current arousal level may become lower as a currentrespiratory rate or a current amount of air breathed becomes lower. Thisis because it is known that a person tends to feel drowsy when therespiratory rate is low or the amount of air breathed is small. Thefirst sensor 30 in this case is a respiration sensor.

The first sensor 30 may detect the current respiratory rate of the userusing, for example, a milliwave sensor that measures the movement of theuser's chest using millimeter waves. Alternatively, the first sensor 30may detect the current respiratory rate of the user, for example, byanalyzing temporal changes in an image of the user's chest capturedusing a camera and measuring the movement of the user's chest. This isbecause the movement of the chest and respiration are related to eachother. Although the first sensor 30 measures the user's chest, a bodypart measured by the first sensor 30 is not limited to this. The firstsensor 30 may measure the movement of a surface of any body part relatedto respiration in order to detect the current respiratory rate of theuser.

Alternatively, the first sensor 30 may detect the current heart rate ofthe user, for example, by measuring a change in a color of the user'sskin using a photodiode. The first sensor 30 can calculate the heartrate of the user because the user's skin reddens when peripheral bloodflow volume increases and the peripheral blood flow volume changes inaccordance with the heart rate.

Alternatively, the first sensor 30 may detect the current respiratoryrate of the user, for example, by measuring a change in the color of theuser's skin using a photodiode. The first sensor 30 can calculate therespiratory rate of the user by measuring the color of the user's skinusing a photodiode or the like because oxygen saturation of the userchanges due to respiration and accordingly the color of the user's skinslightly changes.

The heart rate can be calculated on the basis of a color change of 0.5to 3 Hz, and the respiratory rate can be calculated, for example, on thebasis of an average color (temperature) in a minute.

In addition, because variation in heartbeat changes due to respiration,the respiratory rate may be calculated on the basis of a change in thevariation in heartbeat.

Alternatively, the first sensor 30 may detect the current respiratoryrate, the duration of each breath, or the current amount of air breathedof the user by measuring a current temperature of the user's lips or aportion under the user's nose using a radiation thermometer. This isbecause the temperature of a person's lips or the portion under theperson's nose decreases when the person breathes in and increases whenthe person breathes out (exhaled air is hotter than ambient air). Bymeasuring the current temperature of the user's lips or the portionunder the user's nose using a radiation thermometer, therefore, therespiratory rate, the duration of each breath, or the amount of airbreathed can be detected. Alternatively, the first sensor 30 maycalculate the amount of air breathed on the basis of a differencebetween the temperature of the user's lips or the portion under theuser's nose when the user breathes in and the temperature of the user'slips or the portion under the user's nose when the user breathes outusing a radiation thermometer. This method, in which the first sensor 30detects the current respiratory rate of the user or the current amountof air breathed by the user using a radiation thermometer, is thecheapest noncontact method.

Alternatively, the first sensor 30 may detect the current respiratoryrate of the user or the amount of air breathed by the user using aspeckle camera or a laser Doppler velocimeter. By measuring a flow ofair exhaled from the user's nose or mouth using a speckle camera or alaser Doppler velocimeter, the respiratory rate or the amount of airbreathed can be calculated. This method, in which the first sensor 30detects the current respiratory rate of the user or the current amountof air breathed by the user using a speckle camera or a laser Dopplervelocimeter, is expensive, but the current respiratory rate of the useror the current amount of air breathed by the user can be detected mostaccurately.

Alternatively, the first sensor 30 may detect the current respiratoryrate of the user or the current amount of air breathed by the user bydetecting a sound of the user's breathing using a microphone or apiezoelectric sensor attached to the user's clothes, a seat, or aseatbelt. By incorporating a microphone into an earphone or a portion ofglasses in contact with the user's skin, for example, the sound of theuser's breathing can be detected. This is because the first sensor 30can detect the respiratory rate by measuring the sound of the user'sbreathing detected by the microphone and the amount of air breathed onthe basis of the pitch and length of the sound of the user's breathingdetected by the microphone. This method, in which the first sensor 30detects the current respiratory rate of the user or the current amountof air breathed by the user in the above-described manner, is thecheapest contact method.

Alternatively, the first sensor 30 may detect the current respiratoryrate of the user or the current amount of air breathed by the user bymeasuring the movement of the user's chest using a camera and a TOFsensor. This method for detecting the current respiratory rate of theuser or the current amount of air breathed by the user is advantageousin that the method is a noncontact method and can also be used formeasuring heartbeat.

The first sensor 30 that is a respiration sensor may detect only therespiratory rate or the amount of air breathed, or may detect both therespiratory rate and the amount of air breathed. In the latter case, thefirst sensor 30 can be used by the processing unit 13, which will bedescribed later, to accurately calculate the current arousal level ofthe user.

When Biological Information includes Information indicating Body SurfaceTemperature and Deep-Body Temperature

Alternatively, for example, the biological information may includeinformation indicating the body surface temperature and the deep-bodytemperature of a periphery of a person's body, and the current arousallevel may become lower as a current body surface temperature of theperiphery of the user's body becomes closer to the deep-bodytemperature. This is because it is known that a person tends to feeldrowsy when the temperature of the periphery, which includes the nose,the hands, and the feet, becomes closer to the deep-body temperature.The deep-body temperature can be measured, for example, by measuring thetemperature of the forehead, a side of the neck (where an aorta exists),an armpit, or the like.

The first sensor 30 may be a thermal image sensor, which is used fordetecting the current body surface temperature and the deep-bodytemperature of the periphery of the user's body. Alternatively, thefirst sensor 30 may measure the body surface temperature distribution ofthe user, for example, using a thermopile or a bolometer. This isbecause, in this case, the deep-body temperature can be estimated on thebasis of body surface temperatures of a plurality of body parts andambient temperature. More specifically, this is because it is known thata difference (first difference) between the deep-body temperature andthe temperature of the forehead, a difference (second difference)between the temperature of the forehead and the temperature of thehands, and a difference (third difference) between the temperature ofthe hands and ambient temperature have a certain correlation. That is,the first difference can be estimated by calculating the seconddifference and the third difference, and the deep-body temperature canbe estimated from the first temperature and the temperature of theforehead. If ambient temperature and humidity are known, the processingunit 13, which will be described later, can estimate the sensibletemperature of a person on the basis of the ambient temperature and thehumidity. In this case, whether an increase in the temperature of theperiphery of the user's body is caused by external heat or drowsinesscan be determined, thereby making it possible to estimate the arousallevel more accurately.

When Biological Information includes Information indicating Blood FlowVolume

Alternatively, for example, the biological information may includeinformation indicating the blood flow volume of the periphery of aperson, and the current arousal level may become lower as a currentblood flow volume of the periphery of the user's body becomes larger.This is because it is known that a person tends to feel drowsy when theblood flow volume of the periphery of the person's body is large. Thefirst sensor 30 in this case may be a blood flow sensor.

The first sensor 30 may detect the blood flow volume of the periphery ofthe user's body by measuring the blood flow distribution of the userusing a laser speckle camera as the blood flow sensor. This is becausethe blood flow distribution can be measured on the basis of variation ininterference fringes of laser light.

Alternatively, for example, the biological information may includeinformation indicating pulse wave velocity, and the current arousallevel may become lower as blood pressure and the pulse wave velocitybecome lower.

This is because it is known that a person tends to feel drowsy when thepulse wave velocity is low.

The first sensor 30 in this case may include a blood flow sensor.

The first sensor measures changes in blood flow volume in an artery anda vein in each body part of the user using either a laser speckle cameraor a camera as the blood flow sensor. The periphery of the user's bodyis one of such body parts. The first sensor may calculate the pulse wavevelocity on the basis of a time difference in a change in blood flowvolume between an artery of a measured body part of the user and a veinin the periphery.

Alternatively, for example, the biological information may includeinformation indicating blood pressure, and the current arousal level maybecome lower as the blood pressure becomes lower.

This is because it is known that a person tends to feel drowsy when theblood pressure is low.

The first sensor 30 in this case may include a blood pressure sensor.

The first sensor 30 may detect the blood pressure of the user using theblood pressure sensor.

Alternatively, for example, the biological information may includeinformation indicating the pulse wave velocity and the blood pressure.

When Biological Information includes Information indicating Blink Speedand Movement of Eyes

Alternatively, for example, the biological information may includeinformation indicating the blink speed of the user and the movement ofthe user's eyes, and the current arousal level may become lower as acurrent blink speed of the user becomes lower or a current movement ofthe user's eyes become fewer. This is because it is known that a persontends to feel drowsy when the blink speed of the person is low or themovement of the person's eyes is few.

The first sensor 30 in this case may detect the current blink speed ofthe user or the current movement of the user's eyes by capturing animage of the user's eyes using a camera.

Environment Information Obtaining Unit 12

The environment information obtaining unit 12 obtains currentenvironment information detected by the second sensor 40.

In the present embodiment, the environment information obtaining unit 12communicates with the second sensor 40 directly or through thecommunication unit 15 to obtain the current environment information. Theenvironment information may be information indicating illumination,ambient temperature, CO₂ concentration, wind speed, vibration, or anycombination of these pieces of information. The second sensor may be anillumination sensor, an ambient temperature sensor, a CO₂ concentrationsensor, a wind speed sensor, or a vibration sensor, or may detectenvironment information using any combination of these sensors.

If the environment information includes CO₂ concentration, for example,the second sensor 40 may measure the CO₂ concentration using a CO₂concentration sensor, or may include an infrared light source and alight receiving unit and measure CO₂ concentration using CO₂concentration distribution measuring means that measures CO₂concentration in a certain direction through absorption spectroscopy.

Alternatively, the environment information may include the amount ofsolar radiation. In this case, the second sensor 40 may measure theamount of solar radiation using solar radiation measuring means or athermal image sensor, and the environment information obtaining unit 12may obtain a current amount of solar radiation measured by the secondsensor 40.

If there are a plurality of second sensors 40, the environmentinformation obtaining unit 12 may obtain environment information from asecond sensor 40 selected in accordance with a type, a model, or aninstalled position of a second sensor 40 specified by the user inadvance.

Processing Unit 13

FIG. 2 is a block diagram illustrating a detailed configuration of theprocessing unit 13 illustrated in FIG. 1. FIG. 3 is a diagramillustrating a method for predicting a future arousal level according tothe first embodiment.

The processing unit 13 predicts a future arousal level, which is anarousal level a certain period of time later, on the basis of thecurrent biological information regarding the user obtained by thebiological information obtaining unit 11 and the current environmentinformation obtained by the environment information obtaining unit 12.The certain period of time refers to a few minutes to tens of minutes,namely, for example, two, three, or 10 minutes. If the arousal levelprediction apparatus 10 is mounted on an automobile, the certain periodof time is included in a time taken to arrive at a destination input bythe user to a navigation system installed in the automobile.

In the present embodiment, as illustrated in FIG. 2, the processing unit13 includes a current arousal level calculation unit 131 and a futurearousal level prediction unit 132.

The current arousal level calculation unit 131 calculates the currentarousal level of the user on the basis of the current biologicalinformation regarding the user obtained by the biological informationobtaining unit 11.

The future arousal level prediction unit 132 predicts the future arousallevel, which is the arousal level the certain period of time later, onthe basis of the current arousal level calculated by the current arousallevel calculation unit 131 and the current environment informationobtained by the environment information obtaining unit 12. Morespecifically, the future arousal level prediction unit 132 predicts thefuture arousal level by estimating a rate of decrease in the arousallevel on the basis of how likely it is for a person to become drowsy inan environment indicated by the current environment information andcorrecting the current arousal level to the arousal level the certainperiod of time later using the estimated rate of decrease.

More specifically, as illustrated in FIG. 3, the future arousal levelprediction unit 132 estimates a rate of decrease in the arousal levelindicated by an arrow B, for example, on the basis of how likely it isfor a person to become drowsy in an environment around the userindicated by environment information at a present time t1. The futurearousal level prediction unit 132 then calculates a future arousal levelat a time t2 a certain period of time later using the estimated rate ofdecrease (arrow B) and a current arousal level A at the present time t1.The future arousal level prediction unit 132 can thus predict a futurearousal level by correcting a current arousal level to an arousal levela certain period of time later using an estimated rate of decrease.

If the environment information includes information indicatingillumination and the second sensor 40 is an illumination sensor, forexample, the current environment information may be informationindicating a current illumination around the user. In this case, therate of decrease in the arousal level estimated by the future arousallevel prediction unit 132 becomes higher as the current illuminationindicated by the current environment information becomes lower. This isbecause it is known that a person is unlikely to become drowsy in abright environment.

If the environment information includes information indicating windspeed and the second sensor 40 is a wind speed sensor, for example, thecurrent environment information may be information indicating a currentwind speed around the user. In this case, the rate of decrease in thearousal level estimated by the future arousal level prediction unit 132becomes higher as the current wind speed indicated by the currentenvironment information becomes lower. This is because it is known thata person is unlikely to become drowsy when wind is strong.

If the environment information includes information indicating CO₂concentration and the second sensor 40 is a CO₂ concentration sensor,for example, the current environment information may be informationindicating a current CO₂ concentration around the user. In this case,the rate of decrease in the arousal level estimated by the futurearousal level prediction unit 132 becomes higher as the current CO₂concentration indicated by the current environment information becomeshigher. This is because it is known that a person is unlikely to becomedrowsy when CO₂ concentration around the person is low.

If the environment information includes information indicating vibrationand the second sensor 40 is a vibration sensor, for example, the currentenvironment information may be information indicating a currentvibration around the user. In this case, the rate of decrease in thearousal level estimated by the future arousal level prediction unit 132becomes higher as the current vibration indicated by the currentenvironment information becomes larger. This is because it is known thata person is unlikely to become drowsy when vibration applied to theperson is small and that a person is likely to become drowsy when thefrequency of vibration applied to the person is lower than that ofheartbeat within a range of 10% or when the frequency of vibrationapplied to the person is lower than that of respiration within a rangeof 10%.

If the environment information includes information indicating ambienttemperature and the second sensor 40 is an ambient temperature sensor,for example, the current environment information may be informationindicating a current ambient temperature around the user (e.g., atemperature of a room where the user is currently located). In thiscase, the rate of decrease in the arousal level estimated by the futurearousal level prediction unit 132 becomes higher as the current ambienttemperature indicated by the current environment information becomeshigher. This is because it is known that a person is unlikely to becomedrowsy when ambient temperature is low. Because comfortable temperatureis different between winter and summer, namely 20° C. in winter and 25°C. in summer, whether ambient temperature is high or low may beevaluated on the basis of the comfortable temperature corresponding tothe season.

If the environment information includes information indicating ambienttemperature distribution and the second sensor 40 is a radiationtemperature sensor, for example, the current environment information mayindicate a current ambient temperature distribution around the user(e.g., a temperature distribution in a room where the user is currentlylocated). Because it is known that a person is unlikely to become drowsywhen temperatures around the head, the hands, and the feet are low andtemperatures around the chest and the abdomen are high, the rate ofdecrease in the arousal level estimated by the future arousal levelprediction unit 132 becomes lower as a value obtained by subtracting atemperature around the hands or the feet from a temperature around thechest or the abdomen becomes larger.

A relationship illustrated in FIG. 3 may be obtained, for example, as aresult of experiments for obtaining relationships between the durationof driving and the arousal level in various environments.

If the second sensor 40 detects illumination, for example, theexperiments for obtaining the relationships between the duration ofdriving and the arousal level are conducted while a subject is drivingunder a condition of a constant illumination.

At this time, the experiments for obtaining the relationships betweenthe duration of driving and the arousal level are conducted with variousvalues of the constant illumination.

The same holds when the second sensor 40 detects information other thanillumination, namely, for example, ambient temperature, CO₂concentration, wind speed, or vibration.

In doing so, the relationships between the duration of driving and thearousal level can be obtained in various environments.

The subject may or may not be the user. The number of subjects may beone or more. If there are a plurality of subjects, the relationshipsbetween the duration of driving and the arousal level may be resultsobtained by performing a statistical process, such as averaging, onrelationships between the duration of driving and the arousal levelobtained from the subjects.

The above-described relationships may be associated with environments inwhich experiments have been conducted, for example, and stored in amemory (not illustrated) of the arousal level prediction apparatus 10 inadvance.

The processing unit 13 may read, from the memory, a relationship betweenthe duration of driving and the arousal level corresponding to anenvironment indicated by the current environment information obtained bythe environment information obtaining unit 12 and predict a futurearousal level or estimate a rate of decrease in the arousal level usingthe relationship read from the memory.

Control Unit 14

The control unit 14 (i) issues a notification to the user or (ii)controls another device 20 on the basis of the future arousal level. Thecontrol unit 14 performs the notification or the control only if thefuture arousal level is lower than a certain threshold. The certainthreshold is an arousal level low enough to hinder the user's currentactivity. In order to increase such an arousal level, certain measuresneed to be taken. The other device 20 is a device to be controlled, andmay be an air conditioner or a lighting device, for example, installedin the same space in which the arousal level prediction apparatus 10 isinstalled or a personal computer (PC) including a display unit used bythe user. The other device 20 may be a chair or a steering wheel of anautomobile in contact with the user.

In the present embodiment, the control unit 14 determines whether apredicted future arousal level is lower than the certain threshold. Ifthe predicted future arousal level is lower than the certain threshold,the control unit 14 may output a notification signal to a mobileterminal owned by the user through the display unit 16 or thecommunication unit 15 to display a screen for notifying the user thatthe future arousal level is lower than the certain threshold. In thiscase, the user can try to increase his/her arousal level by drinking acup of coffee or opening a window of the automobile.

If the predicted future arousal level is lower than the certainthreshold, the control unit 14 may output a control signal to the otherdevice 20 through the communication unit 15 to control the other device20 in such a way as to increase the arousal level of the user. If theother device 20 is an air conditioner installed in the same space inwhich the arousal level prediction apparatus 10 is installed, forexample, the control unit 14 may change a setting temperature or an airvolume of the air conditioner when the future arousal level is lowerthan the certain threshold. By blowing cooling air early in this manner,for example, it becomes possible to suppress a decrease in the currentarousal level. A decrease in the arousal level can be further reduced bycooling the periphery of the user's body, namely the face, the hands, orthe feet. It is known that a person tends to feel that ambienttemperature has dropped by 2° C., for example, when the user's head isexposed to a wind of 0.5 m/s.

If the environment information includes information indicating CO₂concentration and the other device 20 is a CO₂ concentration reducingapparatus, such as a ventilation fan, installed in the same space inwhich the arousal level prediction apparatus 10 is installed, forexample, the control unit 14 may activate the CO₂ concentration reducingapparatus such as a ventilation fan when a future arousal level is lowerthan the certain threshold. By reducing the CO₂ concentration early inthis manner, for example, it becomes possible to suppress a decrease inthe current arousal level. If the environment information includesinformation indicating CO₂ concentration and the other device 20 is anoxygen enrichment membrane installed in the same space in which thearousal level prediction apparatus 10 is installed, for example, thecontrol unit 14 may control the oxygen enrichment membrane in such a wayas to increase O₂ concentration or N₂ concentration when a futurearousal level is lower than the certain threshold.

If the other device 20 is a lighting device installed in the same spacein which the arousal level prediction apparatus 10 is installed, forexample, the control unit 14 may increase the brightness of the lightingdevice when a future arousal level is lower than the certain threshold.By increasing the brightness early in this manner, it becomes possibleto suppress a decrease in the current arousal level. A decrease in thearousal level can be further reduced by adjusting the direction of thelighting device in order to increase the amount of light that reachesthe user's eyes.

If the other device 20 is a PC including a display unit used by theuser, for example, the control unit 14 may change a color or luminanceof the display unit of the PC when a future arousal level is lower thanthe certain threshold. The PC may be a head-up display (HUD) or a mobileterminal or an information terminal including a touch panel as a displayunit.

If the other device 20 is a chair or a steering wheel of an automobilein contact with the user, for example, the control unit 14 may generatevibration by activating a driving unit included in the chair or thesteering wheel when a future arousal level is lower than the certainthreshold. Here, if the future arousal level is lower than the certainthreshold but the current arousal level is higher than the certainthreshold, the control unit 14 may activate the driving unit in a firstdriving mode, and if both the future arousal level and the currentarousal level are lower than the certain threshold, the control unit 14may activate the driving unit in a second driving mode, in whichvibration is stronger than in the first driving mode.

If the other device 20 is a music player such as an audio component or aradio cassette player, for example, the control unit 14 may activate themusic player to play music when a future arousal level is lower than thecertain threshold.

If there are a plurality of other devices 20, the control unit 14 mayselect and control one of the other devices 20 in accordance with one ofrules (priority modes) specified by the user in advance. The prioritymodes include, for example, a power-saving priority mode, an arousalinduction priority mode, an ambient temperature comfortability prioritymode, a relaxing mode, and a multiple priority mode. A case will bedescribed hereinafter as an example in which there are a plurality ofother devices 20, namely a lighting device, an air conditioner, and amusic player, installed in the same space in which the arousal levelprediction apparatus 10 is installed.

If the user selects the power-saving priority mode, the control unit 14may select and control the lighting device or the music player asanother device 20, not the air conditioner, whose power consumption ishigh. If the user selects the arousal induction priority mode, thecontrol unit 14 may select and control the air conditioner, whichincreases the arousal level of the user most effectively.

If the user selects the ambient temperature comfortability prioritymode, the control unit 14 may select and control the air conditioner insuch a way as to blow air only to the user's hands, feet, and head sothat the user's comfort is not affected. If the user selects therelaxing mode, the control unit 14 may cause the lighting device tolight up in a warm color so that the user's mental fatigue can bereduced.

If the selects the multiple priority mode, the control unit 14 maycontrol all the other devices 20 including the lighting device, the airconditioner, and the music player.

Communication Unit 15

The communication unit 15 includes a processor and a communicationinterface and has a function of communication with another device 20,which is a device to be controlled, or the like. In the presentembodiment, the communication unit 15 transmits, to the other device 20,a control signal that enables the control unit 14 to control the otherdevice 20. The communication unit 15 also communicates with the firstsensor 30, obtains the current biological information from the firstsensor 30, and transmits the current biological information to thebiological information obtaining unit 11. The communication unit 15 alsocommunicates with the second sensor 40, obtains the current environmentinformation from the second sensor 40, and transmits the currentenvironment information to the environment information obtaining unit12. The communication unit 15 may also communicate with a deviceoperated by the user or the like and receive information indicating apriority mode selected by the user.

Display Unit 16

The display unit 16 is an organic electroluminescence device, a liquidcrystal display, a plasma display panel (PDP), or the like and displaysa control mode of the control unit 14, a calculated current arousallevel, a predicted future arousal level, and the like. The display unit16 may include a touch panel display, which is used for inputtinginformation indicating a priority mode selected by the user anddisplaying the priority mode.

Although the biological information obtaining unit 11 obtains biologicalinformation from the first sensor 30, which is separate from thebiological information obtaining unit 11, and the environmentinformation obtaining unit 12 obtains environment information from thesecond sensor 40, which is separate from the environment informationobtaining unit 12, in the above-described arousal level predictionapparatus 10, the configuration of the arousal level predictionapparatus 10 is not limited to this. As illustrated in FIG. 4, anarousal level prediction apparatus 10A may include a biologicalinformation obtaining unit 11A into which the first sensor 30 isincorporated and an environment information obtaining unit 12A intowhich the second sensor 40 is incorporated. That is, the biologicalinformation obtaining unit 11A may obtain current biological informationregarding the user using a sensor that obtains biological information,and the environment information obtaining unit 12A may obtain currentenvironment information using a sensor that obtains environmentinformation indicating an environment around the user. FIG. 4 is a blockdiagram illustrating the configuration of the arousal level predictionapparatus 10A according to the first embodiment. The same componentsillustrated in FIG. 1 are given the same reference numerals, anddetailed description thereof is omitted.

Operation of Arousal Level Prediction Apparatus 10

Next, the operation of the arousal level prediction apparatus 10 will bedescribed with reference to FIGS. 5 and 6. FIG. 5 is a flowchartillustrating an overall operation of the arousal level predictionapparatus 10 illustrated in FIG. 1. FIG. 6 is a sequence diagramillustrating a procedure of the operation of the arousal levelprediction apparatus 10 illustrated in FIG. 1. In the followingdescription, the other device 20 is an air conditioner 20 a.

First, the arousal level prediction apparatus 10 obtains the currentbiological information regarding the user detected by the first sensor30, which obtains biological information (S1). In the presentembodiment, the biological information obtaining unit 11 communicateswith the first sensor 30 directly or through the communication unit 15and requests biological information from the first sensor 30 (S11). Thebiological information obtaining unit 11 then obtains biologicalinformation from the first sensor 30 (S12).

Next, the arousal level prediction apparatus 10 calculates the currentarousal level of the user on the basis of the obtained currentbiological information (S2).

Next, the arousal level prediction apparatus 10 obtains the currentenvironment information detected by the second sensor 40 that obtainsenvironment information indicating an environment around the user (S3).In the present embodiment, the environment information obtaining unit 12communicates with the second sensor 40 directly or through thecommunication unit 15 and requests environment information from thesecond sensor 40 (S31). The environment information obtaining unit 12then obtains environment information from the second sensor 40 (S32).The processing in steps S2 and S3 need not be performed in this order,but the processing in step S3 may be performed first.

Next, the arousal level prediction apparatus 10 predicts the futurearousal level, which is the arousal level the certain period of timelater, on the basis of the obtained current arousal level and theobtained current environment information (S4).

Next, the arousal level prediction apparatus 10 issues a notification tothe user or controls the other device 20 on the basis of the predictedfuture arousal level (S5). In the present embodiment, first, the controlunit 14 determines whether the predicted future arousal level is lowerthan the certain threshold (S51). Next, if the predicted future arousallevel is lower than the certain threshold (Y in S51), the control unit14 transmits a control signal for changing, say, a setting temperatureof the air conditioner 20 a to the air conditioner 20 a through thecommunication unit 15 (S52).

The air conditioner 20 a then change the setting temperature thereof inaccordance with the received control signal (S6).

If the calculated current arousal level is significantly higher than thecertain threshold, the arousal level prediction apparatus 10 may end theoperation without performing the processing in step S3 and later. Thisis because when it is apparent that the future arousal level will notbecome lower than the certain threshold, the processing need not beperformed.

Advantageous Effects

As described above, according to the present embodiment, the futurearousal level can be predicted, and a method for predicting an arousallevel and an arousal level prediction apparatus capable of detecting adecrease in the arousal level of the user earlier can be achieved. As aresult, the user can be notified of necessary information displayed atan appropriate position at an appropriate timing.

How likely it is for the user to become drowsy in an environment aroundthe user can be calculated using only environment information, and, forexample, whether an office is suitable for work can be evaluated. Whenbiological information is used, however, individual differences betweenusers and a physical condition of the user of the day can be taken intoconsideration, and the future arousal level can be predicted moreaccurately using both the environment information and the biologicalinformation.

In the method for predicting an arousal level and the arousal levelprediction apparatus in the present embodiment, therefore, the futurearousal level is calculated using the current environment informationand the current arousal level calculated from the current biologicalinformation.

As a result, an unnoticed sign of a decrease in the arousal level of theuser can be detected earlier than in a system in the examples of therelated art. The arousal level can be increased without a strongstimulus, and a decrease in the arousal level of the user can besuppressed with a mild stimulus, which is advantageous. That is, sincethe user can be notified on the basis of the future arousal level thatthe arousal level of the user might decrease or another device can becontrolled in such a way as to provide a mild stimulus for maintainingthe arousal level, a decrease in the arousal level of the user can besuppressed.

If the arousal level prediction apparatus 10 is installed in an office,for example, a future arousal level of each user in the office, that is,each worker, is predicted, and ambient temperature around each user, theluminance of a lighting device near each worker, or the like is adjustedin order to create an environment in which each worker is unlikely tobecome drowsy. If the arousal level prediction apparatus 10 is mountedon an automobile, for example, a future arousal level of a user, thatis, a driver of the automobile, is predicted, and an environment inwhich the user is unlikely to become drowsy can be created using avehicle air conditioner, a ventilation system, a vehicle lightingdevice, or the like.

A case in which the arousal level prediction apparatus 10 controls anair conditioner as another device 20 will be described hereinafter. If afuture arousal level is lower than the certain threshold and it can bepredicted that the user is likely to become drowsy, the arousal levelprediction apparatus 10 controls the air conditioner in such a way as todecrease ambient temperature. This is because if the air conditionerdecreases the ambient temperature in order to suppress a decrease in thearousal level even when the user is unlikely to become drowsy, power isnot saved in summer and it is uncomfortable for the user. It istherefore preferable that, as described above, the arousal levelprediction apparatus 10 control the air conditioner on the basis of thepredicted future arousal level. If the arousal level predictionapparatus 10 controls the air conditioner on the basis of the currentarousal level, on the other hand, the ambient temperature decreasesafter the user becomes drowsy, and it is difficult to suppress adecrease in the arousal level of the user. In the present embodiment,since the future arousal level is predicted and cooling air is blownearly, a decrease in the arousal level can be effectively suppressed. Adecrease in the arousal level can be effectively suppressed especiallyby cooling the periphery of the user's body, that is, the user's face,hands, feet, or the like.

Furthermore, the arousal level prediction apparatus 10 may obtain thetemperature of the user's body (especially the periphery) as biologicalinformation. If the user's body (especially the periphery) issufficiently cold, the arousal level can be maintained by controllinganother device without controlling the air conditioner to blow coolingair even when the future arousal level is lower than the certainthreshold and it has been predicted that the user is likely to becomedrowsy. Alternatively, the arousal level prediction apparatus 10 mayobtain the amount of solar radiation on the user as environmentinformation. In this case, because the body temperature of the userincreases when the amount of solar radiation on the user is large, theair conditioner is controlled in such a way as to blow stronger coolingair or cooler air to a side of the user's body exposed to sunlight.

Next, a case will be described in which the environment informationincludes information indicating CO₂ concentration and the arousal levelprediction apparatus 10 controls a CO₂ concentration reducing apparatus,such as a ventilation fan, as another device 20. If the future arousallevel is lower than the certain threshold and it can be predicted thatthe user is likely to become drowsy, the CO₂ concentration reducingapparatus is controlled in such a way as to reduce CO₂ concentration.This is because power is not saved if CO₂ concentration is unnecessarilyreduced in order to suppress a decrease in the arousal level even whenthe user is unlikely to become drowsy. It is therefore preferable that,as described above, the arousal level prediction apparatus 10 controlthe CO₂ concentration reducing apparatus on the basis of the predictedfuture arousal level.

Similarly, a case will be described in which the environment informationincludes information indicating CO₂ concentration and the arousal levelprediction apparatus 10 controls an oxygen enrichment membrane asanother device 20. If the future arousal level is lower than the certainthreshold and it can be predicted that the user is likely to becomedrowsy, the arousal level prediction apparatus 10 may control the oxygenenrichment membrane in such a way as to increase O₂ concentration or N₂concentration. This is because power is not saved if O₂ concentration orN₂ concentration is unnecessarily increased in order to suppress adecrease in the arousal level even when the user is unlikely to becomedrowsy. It is therefore preferable that, as described above, the arousallevel prediction apparatus 10 control the oxygen enrichment membrane onthe basis of the predicted future arousal level.

A case in which the arousal level prediction apparatus 10 controls alighting device as another device 20 will be described hereinafter. Ifthe future arousal level is lower than the certain threshold and it canbe predicted that the user is likely to become drowsy, the arousal levelprediction apparatus 10 may increase the luminance of the lightingdevice. This is because power is not saved if the luminance isunnecessarily increased in order to suppress a decrease in the arousallevel even when the user is unlikely to become drowsy. In summer, inparticular, if the lighting device turns on unnecessarily, an airconditioner needs to cool air heated by the lighting device, which is awaste of power. It is therefore preferable that, as described above, thearousal level prediction apparatus 10 control the lighting device on thebasis of the predicted future arousal level.

The arousal level prediction apparatus 10 may be incorporated into aninformation terminal such as a desktop PC, a laptop PC, or a tablet, anda display of the information terminal may include a camera or noncontactsensors (the first sensor 30 and the second sensor 40), such as thermalimage sensors or milliwave sensors. In this case, by predicting a futurearousal level of the user of the information terminal and increasing thearousal level through adjustment of a color or luminance of the displayof the information terminal or intermittent driving, an environment inwhich the user is unlikely to become drowsy can be created. That is, thearousal level can be maintained by adjusting the color or luminance ofthe display or performing intermittent driving on the basis of thefuture arousal level of the user. The method for controlling anotherdevice is not limited to this. A small blower near the user's desk or aseat heater mounted on the user's chair may be driven by wirelesslytransmitting a result of the prediction, instead. Alternatively,information for controlling each device, not the result of theprediction, based on the result of the prediction may be transmitted.

Second Embodiment

Although the future arousal level is predicted on the basis of thecurrent biological information and the current environment informationin the first embodiment, the method for predicting the future arousallevel is not limited to this. The future arousal level may be predictedon the basis of these pieces of information and living informationregarding the user, such as an activity history. In this case, theaccuracy of predicting the future arousal level improves. This case willbe described hereinafter as a second embodiment.

Configuration of Arousal Level Prediction Apparatus

FIG. 7 is a block diagram illustrating the configuration of an arousallevel prediction apparatus 10B according to the second embodiment. Thesame components as in FIG. 1 or another figure are given the samereference numerals, and detailed description thereof is omitted.

The arousal level prediction apparatus 10B illustrated in FIG. 7 isdifferent from the arousal level prediction apparatus 10 according tothe first embodiment in that a living information obtaining unit 17 isadded and the configuration of a processing unit 13B is different fromthat of the processing unit 13.

Living Information Obtaining Unit 17

The living information obtaining unit 17 obtains information indicatingan activity history. In the present embodiment, the living informationobtaining unit 17 communicates with a living information managementserver 50 directly or through the communication unit 15 and obtainsliving information regarding the user as information indicating anactivity history. The living information obtaining unit 17, for example,may obtain sleep information indicating hours of sleep of the user of aprevious day, past sleep information indicating hours of sleep of theuser in a certain period of time in the past, or information indicatingan activity history of the user of the previous day as livinginformation.

When Living Information indicates Hours of Sleep of Previous Day

The living information, for example, may be sleep information indicatinghours of sleep of the user of the previous day. This is because it isknown that a person tends to feel drowsy when hours of sleep of theprevious day is short. The hours of sleep of the user of the previousday, for example, can be measured by providing a sheet sensor on a bedand measuring a beginning and an end of sleep. Alternatively, amilliwave sensor or an infrared sensor installed in a bedroom may beused as a noncontact sleep meter. In the present embodiment, informationmeasured by the sheet sensor or the sleep meter is transmitted to theliving information management server 50 through communication means asliving information indicating the hours of sleep of the user of theprevious day. The information measured by the sheet sensor or the sleepmeter may be directly obtained by the living information obtaining unit17 as living information indicating the hours of sleep of the user ofthe previous day.

When Living Information indicates Past Sleep Information

Alternatively, for example, the living information may be past sleepinformation indicating hours of sleep of the user in a certain period oftime in the past. The past sleep information includes not only sleepinformation indicating the hours of sleep of the user of the previousday but also information indicating average hours of sleep of the user.This is because necessary hours of sleep varies between individuals anda person whose average hours of sleep is short is unlikely to becomedrowsy even if the hours of sleep of the previous day is short. In thiscase, by dividing the hours of sleep of the previous day by the averagehours of sleep, how likely it is to become drowsy can be calculated. Itcan be determined that the user is likely to become drowsy when thehours of sleep of the user of the previous day is shorter than theaverage hours of sleep of the user by 10% or more.

In the present embodiment, the information measured by the sheet sensoror the sleep meter is transmitted to the living information managementserver 50 through communication means as living information indicatingthe hours of sleep of the user of the previous day. The livinginformation management server 50 manages not only the hours of sleep ofthe user of the previous day but also hours of sleep in the certainperiod of time in the past. As a result, the living informationobtaining unit 17 can obtain not only the hours of sleep of the user ofthe previous day but also the average hours of sleep from the livinginformation management server 50.

When Living Information indicates Previous Mealtime

Alternatively, for example, the living information may be informationindicating a previous mealtime of the user. This is because it is knownthat a person tends to become drowsy after a meal. The previous mealtimeof the user, for example, may be recorded by the user using asmartphone. The method for obtaining a previous mealtime of the user isnot limited to this, but any method may be used insofar as the previousmealtime of the user can be obtained.

When Living Information indicates Amount of Conversation with Others

Alternatively, for example, the living information may be informationindicating the amount of conversation between the user and others. Ifthe amount of speech of of the user is small and the amount of speech ofothers (persons nearby) is large, it can be determined that the user isdrowsy, and if the amount of speech of the user is large, it can bedetermined that the user is not drowsy. Alternatively, the amount ofconversion between the user and others may be measured for 10 minutes ormore, and if the amount of speech of the user had been large until 10minutes ago but the current amount of speech of the user is small, itmay be determined that the user is drowsy.

When Living Information indicates Exercise Logs of User

Alternatively, the living information may be information indicatingexercise logs of the user. This is because a person tends to becomedrowsy after performing a certain amount of exercise or more. If awearable terminal worn by the user, such as a smart watch, and theliving information management server 50 are connected to each other, theliving information obtaining unit 17 may obtain exercise logs recordedin the wearable terminal from the living information management server50. The living information obtaining unit 17 may directly obtain theexercise logs recorded in the wearable terminal in cooperation with thewearable terminal, instead.

When Living Information indicates another Activity History.

Alternatively, for example, the living information may be informationindicated by a scheduler recorded in an information terminal owned bythe user or the like. This is because a person tends to become drowsywhen there have been a lot of tasks. If the information terminal ownedby the user or the like and the living information management server 50are connected to each other, for example, the living informationobtaining unit 17 may obtain the information indicated by the schedulerrecorded in the information terminal owned by the user or the like fromthe living information management server 50. The living informationobtaining unit 17 may directly obtain the information indicated by thescheduler recorded in the information terminal or the like incooperation with the information terminal or the like.

When Living Information indicates Acceleration History or DrivingHistory of the Vehicle

If the arousal level prediction apparatus 10B is mounted on a vehiclesuch as an automobile, the living information may be informationindicating an acceleration history or a driving history of the vehicle.This is because the processing unit 13B, which will be described later,can use this kind of information to accurately calculate the futurearousal level of the user. It is known that, for example, a person tendsto become drowsy when driving on a relatively straight road and isunlikely to become drowsy when driving on a winding road.

Processing Unit 13B

The processing unit 13B predicts a future arousal level, which is anarousal level a certain period of time later, on the basis of thecurrent biological information obtained by the biological informationobtaining unit 11, the current environment information obtained by theenvironment information obtaining unit 12, and the biologicalinformation obtained by the living information obtaining unit 17.

More specifically, if the living information is information indicatingexercise logs of the user and the exercise logs indicate that the userhas performed the certain amount of exercise or more, for example, theprocessing unit 13B may decrease the future arousal level predicted onthe basis of the current arousal level and the current environmentinformation.

If the living information is information indicated by the schedulerrecorded in the information terminal owned by the user or the like andthe scheduler indicates that there have been a lot of tasks, forexample, the processing unit 13B may decrease the future arousal levelpredicted on the basis of the current arousal level and the currentenvironment information.

If the living information is information indicating an accelerationhistory or a driving history of a vehicle, for example, the processingunit 13B may correct the future arousal level predicted on the basis ofthe current arousal level and the current environment information usingan arousal level decrease progress speed estimated on the basis of theacceleration history or the driving history.

Operation of Arousal Level Prediction Apparatus

Next, the operation of the arousal level prediction apparatus 10B willbe described with reference to FIG. 8. FIG. 8 is a flowchartillustrating an overall operation of the arousal level predictionapparatus 10B illustrated in FIG. 7. Processing in steps S21 to S23 andS26 illustrated in FIG. 8 is the same as steps S1 to S3 and S5,respectively, illustrated in FIG. 5, and detailed description thereof isomitted. Processing in steps S24 and S25, which are different from thesteps according to the first embodiment, will be described hereinafter.

In step S24, the arousal level prediction apparatus 10B obtains theliving information regarding the user from the living informationmanagement server 50 or the like. In the present embodiment, the livinginformation obtaining unit 17 communicates with the living informationmanagement server 50 directly or through the communication unit 15 andobtains the living information such as the sleep information indicatingthe hours of sleep of the user of the previous day, the past sleepinformation indicating the hours of sleep of the user in the certainperiod of time in the past, or the activity history of the user of theprevious day.

Next, in step S25, the arousal level prediction apparatus 10B predictsthe future arousal level, which is the arousal level the certain periodof time later, on the basis of the current biological informationregarding the user obtained by the biological information obtaining unit11, the current environment information obtained by the environmentinformation obtaining unit 12, and the biological information obtainedby the living information obtaining unit 17.

Advantageous Effects

As described above, according to the present embodiment, since thefuture arousal level can be predicted, a method for predicting anarousal level and an arousal level prediction apparatus capable ofdetecting a decrease in the arousal level of the user earlier can beachieved. As a result, the user can be notified of necessary informationdisplayed at an appropriate position at an appropriate timing.

More specifically, the method for predicting an arousal level and thearousal level prediction apparatus according to the present embodimentcan predict the future arousal level more accurately using the livinginformation such as the activity history of the user as well as thecurrent environment information and the current arousal level calculatedfrom the current biological information.

Although the method for predicting an arousal level and the arousallevel prediction apparatus predict the future arousal level in the firstand second embodiments, what is predicted is not limited to this. Adegree of drowsiness, fatigue, tension, or anxiousness of the user inthe future may be predicted, instead.

An example of a case in which the drowsiness of the user is predictedwill be described hereinafter.

Because the heart rate, a ratio of an LF component to an HF component ofthe heart rate, that is, LF/HF, and the blood pressure begin to decreasewhen the user begins to become drowsy, these pieces of information aresuitable to detect initial drowsiness (predict drowsiness). Rates atwhich these pieces of information change in accordance with the progressof drowsiness, however, vary between individuals (users). By learningvalues of the heart rate, the LF/HF, and the blood pressure at a timewhen each user is widely awake and at a time when each user issignificantly drowsy (about drowsiness level 4), therefore, the accuracyof predicting drowsiness improves. If the arousal level predictionapparatus in the present embodiment is mounted on an automobile, forexample, the user (driver) is determined to be widely awake about fiveminutes after the user gets in the automobile, and a state of the userwhile the user is driving in a wiggly line is determined as drowsinesslevel 4. Values of the heart rate, the LF/HF, and the blood pressure atthese points in time are then stored. As a result, the accuracy ofpredicting drowsiness improves.

In this example, it is assumed that five drowsiness levels, namelydrowsiness levels 1 to 5, are defined. The state of the user defined bydrowsiness levels 1 to 5, for example, is determined by the processingunit 13 using the information obtained from the biological informationobtaining unit 11, the environment information obtaining unit 12, or theliving information obtaining unit 17 or information obtained from asensor mounted on the automobile (e.g., a sensor that detects a steeringangle), a navigation system, or the like.

Drowsiness level 1, for example, may be a state in which the user iswidely awake.

Drowsiness level 2, for example, is a drowsiness level at which thearousal level of the user is lower (more drowsy) than in drowsinesslevel 1. Drowsiness level 2, for example, is a drowsiness level at whichthe arousal level of the user is higher (less drowsy) than at drowsinesslevel 3.

Drowsiness level 3, for example, is a drowsiness level at which thearousal level of the user is lower than at drowsiness level 2 but higherthan at drowsiness level 4.

Drowsiness level 5, for example, is a drowsiness level at which thearousal level of the user is lower than at drowsiness level 4.

Drowsiness level 5, for example, may be a state in which the user isasleep or the user can be regarded as being asleep.

The processing unit 13 determines that the drowsiness level is 4, forexample, if the processing unit 13 receives, from a navigation system,which is not illustrated, information indicating that the driver iscurrently driving on a straight road and receives information indicatingthat a frequency at which an angle detected by a sensor that detects asteering angle exceeds a certain threshold is higher than a certainfrequency.

If determining that the drowsiness level of the user is 4, theprocessing unit 13 obtains the biological information regarding the userusing the biological information obtaining unit 11 as the currentarousal level of the user and stores the obtained biological informationin the memory (not illustrated) of the arousal level predictionapparatus 10. As a result, the biological information regarding the usercorresponding to drowsiness level 4 can be obtained. The arousal levelof the user corresponding to drowsiness level 4 is then calculated usingthis biological information.

The same holds for drowsiness levels 1, 2, 3, and 5. If determining thatthe state of the user corresponds to each drowsiness level, theprocessing unit 13 obtains the biological information regarding the usercorresponding to each drowsiness level from the biological informationobtaining unit 11 and stores the obtained biological information in thememory (not illustrated) of the arousal level prediction apparatus 10.The processing unit 13 then calculates the arousal level correspondingto each drowsiness level from the biological information.

As a result, drowsiness levels 1 to 5 and the corresponding arousallevels can be associated with each other.

The biological information regarding the user obtained by the biologicalinformation obtaining unit 11 at this time is the number of blinks, theblink speed, the heart rate, or the blood pressure of the user or thelike (multimodal).

With respect to drowsiness levels 2 to 5, it is desirable to store, inthe memory, the biological information regarding the user correspondingto each drowsiness level and information regarding a time taken for aprevious corresponding drowsiness level to change to each drowsinesslevel.

In doing so, for example, in an environment indicated by the environmentinformation obtained by the environment information obtaining unit 12,points corresponding to drowsiness levels 1 to 5 can be plotted in agraph in which a horizontal axis represents time since a beginning ofdriving and a vertical axis represents the arousal level as illustratedin FIG. 3. These points may be substantially aligned with one anotherlike the straight line illustrated in FIG. 3, for example, throughregression calculation.

The biological information (measured values) regarding the usercorresponding to the arousal levels corresponding to drowsiness levels 1to 5, for example, may be obtained through the experiments for obtainingthe relationships between the duration of driving and the arousal levelconducted on the user in various environments and stored in the memory(not illustrated) at the arousal level prediction apparatus 10 inadvance.

If the arousal level of the user is drowsiness level 4, for example, itcan be reliably predicted that the arousal level of the user will changeto drowsiness level 5 in course of time. In order to arouse the userwhose drowsiness level is 4, however, a strong stimulus is necessary. Ifsuch a stimulus is given, the user might be surprised during driving,which might affect the driving operation.

If the certain threshold is set at the arousal level of the usercorresponding to drowsiness level 4 and the control unit 14 gives astimulus to the user using another device 20 after the processing unit13 determines that the current drowsiness level of the user is 4, forexample, the stimulus to be given to the user might be too strong, whichmight affect the driving operation.

In the present embodiment, for example, the processing unit 13 predicts,before the drowsiness of the user actually reaches drowsiness level 4,that the drowsiness level of the user is likely to change to drowsinesslevel 4 in a certain period of time. The control unit 14 then gives astimulus to the user using another device 20.

The stimulus to be given to the user to arouse the user whose drowsinesslevel is 3 is milder than the stimulus to be given to the user to arousethe user whose drowsiness level is 4. That is, if the drowsiness levelof the user is 3, a strong stimulus need not be given to the user toarouse the user, compared to when the drowsiness level of the user is 4.

In addition, the stimulus to be given to the user to arouse the userwhose drowsiness level is 2 is milder than the stimulus to be given tothe user to arouse the user whose drowsiness level is 3. That is, if thedrowsiness level of the user is 2, a strong stimulus need not be givento the user to arouse the user, compared to when the drowsiness level ofthe user is 3.

That is, when the drowsiness level of the user is low (the arousal levelis high), the stimulus to be given to the user to arouse the user ismild.

That is, as the current drowsiness level of the user becomes lower, thestimulus to be given to the user by the control unit 14 by controllingthe other device 20 (an air conditioner or a lighting device) to arousethe user (drowsiness level 1) becomes milder.

When the arousal level of the user is high, for example, the user can,during driving, take a look at a screen of a mobile terminal on which anotification has been issued. If, when the drowsiness level of the useris lower than 4, the processing unit 13 predicts that the drowsinesslevel of the user will change to drowsiness level 4 in a certain periodof time and the control unit 14 notifies the mobile terminal of theprediction, the user can arouse himself.

Although an example in which the certain threshold is set at the arousallevel of the user corresponding to drowsiness level 4 has beendescribed, the certain threshold is not limited to this. The certainthreshold may be associated with an arousal level at which the currentdriving operation of the user is affected.

If the relationships between time (the duration of driving) and thearousal level of the user are stored in the memory (not illustrated) ofthe arousal level prediction apparatus 10 in advance, for example, thearousal level prediction apparatus 10 (e.g., the processing unit 13) maycorrect a relationship using the biological information used forcalculating the arousal level corresponding to drowsiness level 4.

FIGS. 9 and 10 are diagrams illustrating examples in which arelationship between the duration of driving and the arousal level ofthe driver (user) is corrected.

After determining that the drowsiness level is 2, 3, or 4, for example,the processing unit 13 reads, from the memory, a relationship betweentime (the duration of driving) and the arousal level of the usercorresponding to the environment indicated by the environmentinformation obtained by the environment information obtaining unit 12.This relationship, for example, is the relationship indicated by abroken line in FIG. 9 or 10. In FIG. 9, a horizontal axis representstime elapsed since a beginning of driving, and a vertical axisrepresents the arousal level of the user. The processing unit 13determines the arousal level of the user calculated using the biologicalinformation (e.g., the blood pressure, the heart rate, or the like)regarding the user detected when the processing unit 13 has determinedthat the drowsiness level is 4 as an arousal level C₁ at a time t2illustrated in FIG. 9. The processing unit 13 then obtains a straightline that passes through a point identified from the time t2 and thearousal level C₁ and that is parallel to an arrow B. The straight lineis a dash-dot line illustrated in FIG. 9.

An arousal level at a time t1 (arousal level A₁) is then connected to anarousal level corresponding to drowsiness level 2 or 3 using theobtained straight line, and the relationship between time (the durationof driving) and the arousal level of the user corresponding to theenvironment is updated as a relationship indicated by the dash-dot lineillustrated in FIG. 9 and stored in the memory. The foregoingrelationship may thus be updated to a relationship suitable for eachuser.

Alternatively, when an arousal level A₂ at the time t1 is the arousallevel corresponding to drowsiness level 2 or 3 calculated by theprocessing unit 13 and the arousal level C₁ at the time t2 is thearousal level corresponding to drowsiness level 4 calculated by theprocessing unit 13, the inclination of the arrow B illustrated in FIG.10 may be corrected to the inclination of a straight line connectingthese two actually calculated arousal levels. The straight line is adash-dot line illustrated in FIG. 10. The straight line, which is thedash-dot line, is parallel to an arrow B₁ illustrated in FIG. 10. Inthis case, a value obtained by subtracting the time t1 from the time t2is a time taken for drowsiness level 2 or 3 to actually change todrowsiness level 4.

The processing unit 13 may thus feed the arousal level of the usercalculated using the biological information (e.g., the blood pressure,the heart rate, or the like) regarding the user detected when theprocessing unit 13 has detected that the drowsiness level is 4 back tocorrect the arousal level corresponding to drowsiness level 2, thearousal level corresponding to drowsiness level 3, or the inclination ofthe straight line indicated by the broken line in FIG. 10.

By performing correction in this manner, the relationship between theduration of driving and the arousal level of the user can be correctedto a relationship according to characteristics of the user.

If there are a plurality of users who drive a single automobile, theautomobile or the arousal level prediction apparatus desirably includesa driver identification unit (not illustrated) that identifies a driver,and the driver identification unit desirably identifies the driver. Theprocessing unit 13 desirably corrects the relationship indicated by thebroken line in FIG. 9 or 10 to a relationship according tocharacteristics of the identified driver (the relationship indicated bythe dash-dot line).

In doing so, drowsiness can be predicted in accordance with thecharacteristics of each user.

Some of the parameters (the heart rate, the LF/HF, the blood pressure,the frequency of blinks, the blink speed, and the like) used forpredicting drowsiness begin to change at an initial stage of drowsiness(when the drowsiness level is low) but rates of change thereof greatlyvary between individuals. The heart rate and the blood pressure are suchexamples. At the initial stage of drowsiness, therefore, the heart rateand the blood pressure may be used as parameters for predictingdrowsiness. When a plurality of parameters are measured, the accuracy ofpredicting drowsiness at the initial stage of drowsiness improves, whichis desirable.

On the other hand, the frequency of blinks and the blink speed hardlychange at the initial stage of drowsiness (drowsiness level 1 or 2)compared to the heart rate or the like but might greatly change when thedrowsiness level is high (drowsiness level 2 to 4).

After the drowsiness level becomes high (e.g., drowsiness level 3 orhigher), therefore, the frequency of blinks and the blink speed may beadded as parameters for predicting drowsiness.

In addition, a camera may be used for predicting drowsiness. In thiscase, the blink speed, a ratio of a period for which the user's eyes areopen to a period for which the user's eyes are closed, and facialexpressions can be measured in a noncontact manner. As a result, aplurality of parameters relating to drowsiness, such as the blink speed,the ratio of the period for which the user's eyes are open to the periodfor which the user's eyes are closed, the facial expressions, the heartrate, the respiration, the blood pressure, an attitude, and the LF/HF,can be measured in a noncontact manner, thereby accurately predictingdrowsiness.

Although the processes in the present disclosure have been describedwith reference to the first and second embodiments, a subject or anapparatus that performs each process is not particularly limited. Forexample, the arousal level prediction apparatus may include a biologicalinformation obtaining unit, an environment information obtaining unit, aprocessing unit, and a control unit as described above, but may includeonly a processing unit and a control unit, instead. Alternatively, theprocessing originally performed by the arousal level predictionapparatus may be performed by a cloud server provided in a placedifferent from a place where the local apparatus is provided, instead.For example, the cloud server and the local apparatus may shareprocessing and control, that is, for example, the cloud server mayperform heavy processing and control and the local apparatus may performlight processing and control. The cloud server and the local apparatusmay be collectively referred to as an “arousal level predictionapparatus”.

Alternatively, the processing originally performed by the arousal levelprediction apparatus may be performed by a processor (described later)incorporated into a particular locally provided apparatus or the like,instead.

(1) The arousal level prediction apparatus is specifically a computersystem including a microprocessor, a read-only memory (ROM), arandom-access memory (RAM), a hard disk unit, a display unit, akeyboard, and a mouse. The RAM or the hard disk unit stores a computerprogram. When the microprocessor operates in accordance with thecomputer program, the arousal level prediction apparatus achieves thefunctions thereof. The computer program is a combination of a pluralityof command codes for issuing instructions to a computer in order toachieve the functions.

(2) Part or all of the components of the arousal level predictionapparatus may be achieved by a single system large-scale integration(LSI) circuit. The system LSI circuit is a super-multifunctional LSIcircuit fabricated by integrating a plurality of components on a singlechip and, more specifically, a computer system including amicroprocessor, a ROM, and a RAM. The RAM stores a computer program.When the microprocessor operates in accordance with the computerprogram, the system LSI circuit achieves functions thereof.

(3) Part or all of the components of the arousal level predictionapparatus may be achieved by an integrated circuit (IC) card removablyattached to an apparatus or a separate module. The IC card or the moduleis a computer system including a microprocessor, a ROM, and a RAM. TheIC card or the module may include the above-mentionedsuper-multifunctional LSI circuit. When the microprocessor operates inaccordance with the computer program, the IC card or the module achievesfunctions thereof. The IC card or the module may be tamper-resistant.

(4) The present disclosure may be the above-described methods.Alternatively, the present disclosure may be a computer program withwhich a computer achieves these methods, or a digital signal includingthe computer program.

(5) Alternatively, the present disclosure may be a computer-readablerecording medium, namely, for example, a flexible disk, a hard disk, acompact disc read-only memory (CD-ROM), a magneto-optical (MO) disk, adigital versatile disc (DVD), a DVD-ROM, a DVD-RAM, a Blu-ray Disc (BD;registered trademark), or a semiconductor memory, storing the computerprogram or the digital signal. Alternatively, the present disclosure maybe the digital signal recorded on one of these recording media.

Alternatively, the present disclosure may be the computer program or thedigital signal transmitted through an electrical communication line, awireless or wired communication line, a network typified by theInternet, datacasting, or the like.

Alternatively, the present disclosure may be a computer system includinga microprocessor and a memory. The memory may store the computerprogram, and the microprocessor may operate in accordance with thecomputer program.

Alternatively, the present disclosure may be implemented by anindependent computer system using the computer program or the digitalsignal transported in one of the recording media or through the networkor the like.

(6) The above embodiments and modifications may be combined with oneanother.

The present disclosure is effective as a method for predicting anarousal level and an arousal level prediction apparatus that are used ina vehicle, an airplane, an office, an information terminal apparatus, orthe like and that predict a future arousal level of the user.

What is claimed is:
 1. A method for predicting an arousal level used bya computer of an arousal level prediction apparatus that predicts anarousal level of a user, the method comprising: obtaining currentbiological information regarding the user detected by a first sensor;calculating a current arousal level of the user on the basis of thecurrent biological information; obtaining current environmentinformation indicating a current environment around the user detected bya second sensor; predicting a future arousal level, which is an arousallevel a certain period of time later, on the basis of the currentarousal level and the current environment information; and (i) issuing anotification to the user or (ii) controlling another device, on thebasis of the future arousal level.
 2. The method according to claim 1,wherein, in the predicting a future arousal level, a rate of decrease inthe arousal level is estimated on the basis of how likely it is for aperson to become drowsy indicated by the current environmentinformation, and wherein the future arousal level is predicted bycorrecting the current arousal level to the arousal level the certainperiod of time later using the rate of decrease.
 3. The method accordingto claim 1, wherein the issuing or the controlling is performed only ifthe future arousal level is lower than a certain threshold.
 4. Themethod according to claim 1, wherein the arousal level predictionapparatus is mounted on an automobile, and wherein the certain period oftime is included in a time taken to arrive at a destination input by theuser to a navigation system installed in the automobile.
 5. The methodaccording to claim 1, wherein the biological information includesinformation indicating a heart rate, and wherein the current arousallevel becomes lower as a current heart rate of the user becomes lower.6. The method according to claim 5, wherein the first sensor detects thecurrent heart rate of the user using any of a milliwave sensor, a pulseoximeter, a speckle camera, and a laser Doppler velocimeter.
 7. Themethod according to claim 1, wherein the biological information includesinformation indicating a respiratory rate or an amount of air breathed,and wherein the current arousal level becomes lower as a currentrespiratory rate of the user becomes lower or a current amount of airbreathed by the user becomes smaller.
 8. The method according to claim7, wherein the first sensor detects the current respiratory rate of theuser by measuring a change in a color of the user's skin using aphotodiode.
 9. The method according to claim 7, wherein the first sensordetects the current respiratory rate of the user or the current amountof air breathed by the user by measuring a current temperature of theuser's lips or a portion under the user's nose using a radiationthermometer.
 10. The method according to claim 1, wherein the biologicalinformation includes information indicating a body surface temperatureof a periphery of a person's body and a deep-body temperature, andwherein the current arousal level becomes lower as a current bodysurface temperature of a periphery of the user's body becomes closer tothe deep-body temperature.
 11. The method according to claim 1, whereinthe biological information includes information indicating a blood flowvolume in a periphery of a person's body, and wherein the currentarousal level becomes lower as a current blood flow volume in aperiphery of the user's body becomes larger.
 12. The method according toclaim 11, wherein the first sensor detects the current blood flow volumein the periphery of the user's body by measuring blood flow distributionof the user using a laser speckle camera.
 13. The method according toclaim 2, wherein the current environment information includesinformation indicating a current illumination around the user, andwherein the rate of decrease in the arousal level becomes higher as thecurrent illumination becomes lower.
 14. The method according to claim 2,wherein the current environment information includes informationindicating a current wind speed around the user, and wherein a higherrate of decrease in the arousal level is estimated as the current windspeed becomes lower.
 15. The method according to claim 1, furthercomprising: obtaining sleep information indicating hours of sleep of theuser of a previous day; and predicting the future arousal level on thebasis of the current arousal level, the current environment information,and the sleep information.
 16. The method according to claim 1, furthercomprising: obtaining past sleep information indicating hours of sleepof the user in a certain period of time in past; and predicting thefuture arousal level on the basis of the current arousal level, thecurrent environment information, and the past sleep information.
 17. Themethod according to claim 1, further comprising: obtaining informationindicating an activity history of the user; and predicting the futurearousal level on the basis of the current arousal level, the currentenvironment information, and the activity history.
 18. The methodaccording to claim 1, wherein the other device is an air conditionerinstalled in the same space in which the arousal level predictionapparatus is installed, and wherein setting temperature or air volume ofthe air conditioner is changed if the future arousal level is lower thana certain threshold.
 19. The method according to claim 1, wherein theother device is a lighting device installed in the same space in whichthe arousal level prediction apparatus is installed, and whereinbrightness of the lighting device is increased if the future arousallevel is lower than a certain threshold.
 20. The method according toclaim 1, wherein the other device is a personal computer including adisplay used by the user, and wherein a color or luminance of thedisplay of the personal computer is changed if the future arousal levelis lower than a certain threshold.
 21. The method according to claim 1,wherein a processor included in the computer performs at least any ofthe obtaining current biological information, the calculating a currentarousal level, the obtaining current environment information, thepredicting a future arousal level, and the issuing a notification to theuser or the controlling another device.
 22. An arousal level predictionapparatus comprising: a first sensor that detects biologicalinformation; a second sensor that detects environment informationindicating an environment around a user; a processor that calculates acurrent arousal level of the user on the basis of current biologicalinformation regarding the user detected by the first sensor and thatpredicts a future arousal level, which is an arousal level a certainperiod of time later, on the basis of the current arousal level andcurrent environment information detected by the second sensor; and acontroller that (i) issues a notification to the user or (ii) controlsanother device, on the basis of the future arousal level.